A general magnetic recording and/or reproducing apparatus such as a video tape recorder (VTR) records and reproduces information by way of a magnetic tape being scanned obliquely by a rotary head for high density recording. Thus, in a conventional VTR, as shown in FIG. 1, rotary heads H1, H2, . . . Hn and primary windings N11, N21, . . . Nn1 of rotary transformers T1, T2, . . . Tn are mounted on an upper rotary cylinder A of head drum while secondary windings N12, N22, . . . Nn2 of rotary transformers T1-Tn are mounted on a downside stationary cylinder B. The rotary heads are electrically connected through the rotary transformers to a head switching and preamplifier circuit C. Accordingly, equal numbers of rotary transformers and rotary heads are placed in a concentric circular pattern on a plane for a tight coupling between the primary and secondary windings of the rotary transformers. Here, the primary windings of each rotary transformer are placed in a concentric circular pattern in the lower part of the upper cylinder and the secondary windings of each rotary transformer are placed in a concentric circular pattern in the upper part of the lower cylinder.
Table 1 shows the number of heads used in various models of rotary head type VTRs. It will be noted that the number of heads increases for multifunction and high-quality VTRs, which restricts installation space for rotary transformers having a planar configuration.
TABLE 1 ______________________________________ Model type Head Video head Audio head Erasing head ______________________________________ 2-head 2 2 -- -- 4-head 4 4 -- -- 4-head hi-fi 6 4 2 -- 4-head 7 4 2 1 advanced A 4-head 9 6 2 1 advanced B ______________________________________
Since the intervals between windings decreases when the number of heads increases, a degradation of signal-to-noise (S/N) ratio is caused by cross-talk between the transformers. Therefore, the circuit design for signal processing is more complex and more expensive.
To address this problem, vertically mounted tiers of rotary transformers are disclosed in U.S. Pat. Nos. 4,639,805 and 5,019,926. An alternative approach using optical transmission means instead of a rotary transformer is disclosed in Japan Patent Sho 58-45604.
On the other hand, U.S. Pat. No. 4,926,273 discloses transmission of an information signal, an operational power signal and a control signal through rotary transformer using a time sharing system. An amplifier and a head switching circuit are installed in the upper cylinder of the head drum for a tight coupling between head and amplifier. However, since the power signal is not supplied during the signal transmission period in the disclosed time sharing system, a bulky charging circuit and a power stabilizing circuit are necessary in order to supply enough power to the circuitry in the upper rotary cylinder. Therefore, the circuit configuration becomes complex.
The present invention was motivated by a desire to overcome the problems in the prior art.